1. Field of the Invention
This invention relates to a system and method for molding parts, and more particularly, a system and method for molding parts from contaminated molding materials using a single thermal heat rise.
2. Description of Related Art
In the field of thermoplastic molding, it is common to mold parts using either an injection or compression molding process. Due to the size of the orifices used in the injection molding equipment, it is often difficult to injection mold with reinforcing fibers, such as glass fibers, having a length over one-eighth inch because such fibers are not easily injected into or conveyed through the injection mold equipment. In addition, it is difficult to use contaminated molding materials such as those collected in plastics recycling programs unless they have been substantially cleaned, processed and put into a usable form and size prior to being used in the injection molding equipment. Such cleaning and processing are expensive and can substantially increase the cost of using the contaminated materials, thereby making them economically impractical.
Another problem with the thermoplastic processes of the past is that the thermoplastics become degraded and lose, for example, their strength when exposed to multiple heat rises.
In general, there are two basic types of compression molding processes which may be used for molding thermoplastics. First, a sheet molding process involves placing a reinforcement, such as a glass mat, between sandwiching layers of a thermoplastic and heating the materials to produce a single sheet of material. The single sheet of material is then cut to the desired size and then reheated to molding temperature before being placed in a compression molding press. This process has the disadvantage of higher cost because of the apparatus required, the material handling costs incurred in making the sheet, handling and cutting the sheet, and the like. The material used to make the sheet is also subject to three thermodynamic cycles, a first cycle when the thermoplastic sheet is formed, a second cycle when the thermoplastic sheets and glass mat are molded together, and a third cycle when the resulting sheet is heated to molten temperature prior to molding the part.
The second form of thermoplastic compression is bulk molding compounds by producing a billet of molten material that is placed into a compression molding press which molds the molten material into a part. Effectively placing and distributing long reinforcing fibers in the billet has heretofore required complex machinery. For example, U.S. Pat. No. 5,165,941 issued to Ronald C. Hawley on Nov. 24, 1992, discloses an extruder apparatus and process for compounding thermoplastic resin and fibers. The Hawley extruder includes an apparatus for compounding thermoplastic resin and reinforcing fibers incorporating a resin extruder in which thermoplastic resin pellets are melted in a second, compounding, extruder in which the molten thermoplastic resin is mixed in intimate contact with long reinforcing fibers. The melted thermoplastic resin is not fed into the device with the fibers, but rather is introduced into the compounding extruder at a point downstream of the inlet point for reinforcing fibers, so that the fibers are mechanically worked and heated before coming into contact with heated, molten thermoplastic resins.
The Hawley device generally suffers from complexity that raises the investment and maintenance costs.
The compression molding of products using polymeric material and glass fibers has traditionally produced a material referred to as fiber glass reinforced plastic. This material exhibits characteristics better than the reinforced plastics, but does not exhibit strength, elasticity or impact resistance comparable to thermoplastic materials which are specifically designed to exhibit these characteristics. Most fiberglass reinforced plastic currently in the market is thermoset and is essentially a solidified mixture of fiber glass and plastic without benefit of chemical bonding or specific methods of enhancing polymer entrapment of the glass fibers because the glass fibers are merely immobilized in the resin in which it is embodied.
In addition, thermoset materials are generally not recyclable other than as filler materials, while thermoplastic materials can be remelted and remolded.
In the field of molded parts, many products are currently made from a variety of materials using moldable plastic. In the sporting goods field for example, bicycles, basketball backboards, toy vehicles and the like are commonly produced using multiple plastic materials. Compression molding has been a common method for producing basketball backboards and related parts of basketball goal assemblies, such as the support pull for the basketball backboard for many years. Heretofore, compression molding of basketball backboards and related parts has typically been limited to thermoset materials, which is characterized by placement of a cold charge in a compression mold. Thermoset process materials have certain drawbacks, including the fact that these material are generally not recyclable other than as filler materials. In general, there are two basic types of compression molding processes which may be used for molding thermoplastics. The following description of these two processes outline some of the difficulties that have prevented use of compression molding thermoplastics in the basketball goal assembly field.
The first type is a sheet molding process that involves a reinforcement, such as a glass mat, between sandwiching layers of a thermoplastic and heating the materials to produce a single sheet of material. The single sheet of material is then cut to the desired size and then reheated to molding temperature before being placed in a compression molding press. This process has the disadvantage of higher cost because of the apparatus required, the material handling cost incurred in making the sheet, handling and cutting the sheet, and the like. The material used to make the sheet is also subject to three thermodynamic cycles, a first cycle when the thermoplastic sheet is formed, a second cycle when the thermoplastic sheets and glass mat are molded together, and a third cycle when the resulting sheet is heated to molted temperature before molding the part.
A second form of thermoplastic compression is bulk molding compounds by producing a billet of molten material that is placed into a compression molding press which molds the molten material into a part. Effectively, placing and distributing long reinforcing fibers in the billet has heretofore required complex machinery as discussed in detail in parent application Ser. No. 08/220,906, now issued as U.S. Pat. No. 5,591,384.
In addition, in recent years it has been increasingly common to provide graphics on the front face of molded parts, including the backboard, for a variety of reasons, such as aesthetic appeal to the consumer, product and source identification, and the like. However, the only commercially acceptable method of applying graphics have been silk-screened with inks or by applying decals.
Silk-screening is time consuming and tends to fade after prolonged exposure to sunlight and the elements. Decals are also expensive and can peel off after time.
An example of a prior art basketball backboard with silk-screen graphics is a backboard sold as xe2x80x9cShurShotxe2x80x9d. The silk-screen ShurShot backboard is believed to be about 48 inches across and mates a structurally foam polystyrene molded in a multiple-port injection process. The backboard is molded in the natural color of polystyrene, which is milky white. The entire ShurShot backboard is subsequently spray painted both to seal the polystyrene and to protect the backboard from ultraviolet radiation. Finally, graphics are silk-screened on the front face of the backboard.
In some prior art applications, a graphics display was printed on a styrene sheet and laid by hand into a mold for forming the backboard. Alignment of the sheet was accomplished by aligning holes in the sheet on pins in the mold provided for producing the mounting holes in the backboard. Upon injecting styrene into the mold, the back portion of the graphics sheet melted to cause it to be joined to the face of the backboard. As styrene is relatively easy to print on, its use in this prior art process was conducive to the production of backboards provided with sheets having graphics printed thereon.
One of the problems encountered with printing on parts or backboards molded using the system of the parent application Ser. No. 08/220,906 was that printing on polyolefin materials was difficult because the polyolefin-based materials were relatively non-porous and, therefore, not receptive to printing inks.
What is needed, therefore, is an apparatus and method for molding thermoplastic parts which is simple and economical and which preserves the length of the reinforcing fibers, evenly distributes the reinforcing fibers or any other filler materials while maintaining flexibility of the material type in products fabricated, is capable of capitalizing on use of various contaminated thermoplastics to allow use of post consumer recycled material, and which provides a compounding and fabrication environment which promotes chemical bonding and molecular orientation to enhance the characteristics of the molded part.
The foregoing also demonstrates the need for a compression molding apparatus and method for making parts, such as sporting goods equipment including basketball backboards from recycled thermoplastic materials without requiring the extensive cleaning and processing that heretofore has made use of thermoplastics for these products in practical. There is also a need to improve the in-mold graphics process to permit the basketball backboard and other plastic molded parts of basketball goal assemblies to be compression molded with thermoplastic resin materials having improved in-molded graphics.
It is therefore a primary object of this invention to provide a method and apparatus which facilitates overcoming one or more of the aforementioned problems.
In one aspect of the invention, this invention comprises a plasticator for creating a billet of moldable material including a feeder for receiving a plurality of molding materials comprising a predetermined amount of a polyester, other carbocyclic and reinforcing fibers and a suspender coupled to said feeder for receiving the molding materials, for creating a molten suspension of the molding materials without damaging a substantial number of the reinforcing fibers, and also for creating the billet.
In one aspect of the invention, this invention comprises a plasticator for creating a billet of moldable material including a feeder for receiving a plurality of molding materials comprising a predetermined amount of a polyester, other carbocylics and reinforcing fibers, and a suspender coupled to the feeder for receiving the molding materials, for creating a molten suspension of the molding materials without damaging a substantial number of the reinforcing fibers, and also for creating the billet.
In another aspect of the invention, this invention comprises a method for creating a billet for molding a part comprising the steps of (a) loading a plasticator with molding materials, the molding materials comprising a polyester, other carbocylics and reinforcing fibers, (b) heating the molding materials to a predetermined temperature, (c) blending the molding materials in order to create a molten suspension wherein a majority of the reinforcing fibers remain generally undamaged, and (d) extruding the molten suspension in order to form a billet having preselected billet characteristics.
In yet another aspect, this invention comprises a plasticator for creating a billet from a plurality of molding materials, the plasticator comprising plasticating means for receiving the molding materials and for creating a molten suspension of the molding materials, and control means associated with the plasticating means for controlling the suspension characteristics applied to the molding materials in order to plasticity the plurality of molding materials into a billet having predetermined billet characteristics.
In still another aspect, this invention comprises a system for molding a part comprising a plasticator for creating a billet from a plurality of molding materials, the plasticator comprising plasticating means for receiving the molding materials and for creating a molten suspension of the molding materials, control means associated with the plasticating means for controlling the suspension characteristics applied to the molding materials in order to plasticity the plurality of molding materials into a billet having predetermined billet characteristics, and a press having a mold for receiving the billet and for molding the billet into the part.
In yet another aspect, this invention comprises a plasticating process comprising the steps of loading a plasticator with a plurality of molding materials, creating a mixture with the plurality of molding materials in the plasticator, and plasticating the mixture of the plurality of molding materials at a controlled temperature and pressure in order to create a billet having predetermined billet characteristics.
In a still further aspect, the invention comprises a screw for use in a plasticator having a barrel, the screw comprising a root and a plurality of threads configured to permit a polyester, other carbocylics and a plurality of reinforcing fibers to be mixed to provide a billet having predetermined billet characteristics without damaging a substantial number of the reinforcing fibers.
It is an object of this invention to provide a system and method for using long reinforcing fibers that can be loaded simultaneously along with the thermoplastics being used.
Another object is to facilitate providing a system and method which is simple and economical and which provides a process that generally preserves the length of the reinforcing fibers through the plasticating and molding process.
Another object of this invention is to provide a method and apparatus which evenly distributes any filler materials, such as reinforcing fibers, which are used in the apparatus and method.
Still another object of the invention is to provide a method and apparatus which facilitates using contaminated molding materials which have heretofore been undesirable for use because of their contamination or because they are expensive to clean sufficiently for use.
Still another object of this invention is to provide a method and apparatus which facilitates or enhances chemical bonding and molecular orientation of the polymer molding materials being used.
Yet another object is to provide a system and method for efficiently and effectively in-molding graphics into a part such as a basketball backboard or other sporting equipment.
In a still further aspect of the invention this invention comprises a plasticating process comprising the steps of loading a plasticator with a plurality of molding materials, creating a mixture with the plurality of molding materials in the plasticator, and plasticating the mixture of said plurality of molding materials at a controlled temperature and pressure in order to create a billet having predetermined billet characteristics.
In another aspect of the invention a process for molding a part comprises the steps of placing a sheet into a mold prior to molding, placing a billet onto the sheet, compression molding the sheet and the billet to produce a part such that the sheet becomes integrally molded with the part.
In another aspect of the invention a molded part comprising a compression molded part molded from a plurality of materials comprising a predetermined amount of a reinforcing fiber and thermoplastic polymers, a sheet integrally molded into said part, the sheet comprising a graphics side facing away from the part.
In still another aspect of the invention a basketball backboard comprising a backboard member molded from a plurality of materials comprising a predetermined amount of a reinforcing fiber and thermoplastic polymers, and a sheet integrally molded into the backboard member, the sheet comprising a graphics side facing away from the part.
These objects and others will be more apparent when the following description is read in conjunction with the claims and drawings.